Karst terrains represent specific and highly complex hydrogeological, engineering, and environmental geological conditions that pose several potential hazards particularly if there are no restrictions on their landuse practices. The scenario in Lusaka offers such a classic example of a city almost wholly constructed on karstified marble. The presence of a cutter-and-pinnacled rockhead in the Lusaka marbles has caused a lot of foundation design and construction problems resulting from the casting of substructures for the same superstructure on soil and rock. Coupled with inadequate ground investigations, inadequate foundation design and construction practices, as well as increased anthropogenic activities such as those related to groundwater mining, these conditions pose a lot of performance risks to completed engineering structures.
Construction in areas underlain by carbonate rocks can be environmentally risky and economically infeasible unless the possible solutioning-related problems can be identified in advance of project planning, design, and construction (FISCHER et aI., 1989). For Lusaka, inaugurated Zambia''s, then Northern Rhodesia''s new capital on 31st May 1935, the suitability of its location still remains a source of controversy today as it was during the early years of its founding in the beginning of the 1900s. This controversy originates from a number of factors, the major one being the nature of bedrock that underlies the city.
Lusaka is underlain by a Paleo- to Meso-Proterozoic crystalline Basement Complex comprising quartzites and schists. This is unconformably overlain by strongly folded Neo-Proterozoic metasedimentary cover rocks that are dominated by thick and extensive sequences of dolomitic marbles with thin horizons of schists and quartzites. This appears to explain, among others, the general thickening of the dolomitic marbles from NE to SW, and fracturing that has been observed along marble-schist contacts.
